ABSTRACT Transseptal (TS) access for left heart procedures is an important and rapidly growing area for diagnostics and therapy delivery with an expected total of over 10 million U.S. patients. In the U.S. and Europe, TS access procedures are used for atrial fibrillation ablation, left atrial appendage occlusion and patent foramen ovale closure as well as treatment of mitral valve regurgitation with the MitraClip (MC). Catheter positioning and device placement for MC has been challenging even for the most experienced interventionalist cardiologists (ICs) and has led to long procedure times with significant x-ray exposure. This emerging therapy necessitates a higher level of catheter stability and control over accuracy during puncture of the fossa ovalis (FO). If the initial puncture is inaccurate, delivery of therapy is virtually impossible which often requires removal, re-engagement and device re-advancement. Thus, initial localization and stabilization on the FO is critical for MC procedures to limit delivery times and x-ray exposure. Additionally, the presence of aneurysmal or fibrotic FO and the constant movement of the heart makes standard TS access puncture unpredictable and contributes to increased risk for atrial or aortic perforation. To overcome these limitations, we have developed and validated the performance and utility of a novel transseptal access catheter (TSAC) that utilizes vacuum suction technology to provide improved catheter localization and stabilization of the FO. The results of our preclinical studies were highly successful and support that through stabilization of the FO (4-fold reduction in puncture force), the TSAC reduces tenting (2.5-fold) to improve puncture accuracy (1.5-fold) compared to standard TS access devices in a clinically relevant animal model of mitral regurgitation. In this Phase II application, we propose an investigational device exemption (IDE) to conduct a human pilot study which will be used to assess primarily device safety and secondarily device feasibility in patients undergoing TS access for MC delivery. To accomplish these Phase II objectives, the following specific aims are proposed: 1) Final Animal Validation: To assess the safety of the TSAC in a set of animals under good-laboratory practice (GLP) conditions to be used for data submission to the FDA and institutional review boards (IRBs); and 2) Human Validation: To assess the contribution of human factors to feasibility in a small group of humans (36 patients) in a double-arm multi-center study. This Phase II study addresses a highly significant national and worldwide clinical need that can impact not just NHLBI, but many other mission areas of NIH. Successful completion of these proposed Aims will allow us to translate our research findings to a commercially available device that could drastically improve TS access procedures and hence, patient outcomes.